Often, multiple data type exchanges must occur between a transmitter and a receiver in a communication system. For example, in an ink-jet printer subsystem, image data and command data are sent by a host processor such as a personal computer (PC) or file server to the printer for interpretation of the commands and printing of the image data by the printer's controller. Conventionally, such command interpretation and image data printing are performed under firmware control on a byte-by-byte basis. Because printer subsystems are connected to a variety of host processors via a variety of IO ports using a variety of protocols, e.g. Multiple Logical Channels are used with many ink-jet and laser-jet printer products from Hewlett-Packard Co. and layered network architectures such as Internet and AppleTalk.TM. are used in many data communications systems, it is difficult to construct a single scheme for such multiple-device communications. Most prior art solutions also require dedicated hardware in the host processor, as well as substantial memory and software or code. Finally, most prior art solutions require bidirectional IO hardware support.